Telecommunications cables such as electrical cables are typically connected to jacks using modular plugs. The cables are normally comprised of a number of insulated wire pairs surrounded by a cable jacket. Cable assemblies may be constructed by securing modular plugs to the ends of the cable wires. Then a plug is slid into a matching cavity of a jack and secured therein with a snap-fit interlock, normally involving a flexible lever-like latch. The modular plug is inserted into the jack cavity to establish electrical connection between the cable wires terminated to the plug and conductive elements in the jack. A registered jack (e.g., RJ45) type modular plug is one example of a plug that can be used in constructing such cable assemblies.
Typically, a modular plug includes a polymeric housing that defines a front termination end and a rear end that has a cable receiving opening. Adjacent the front end within the housing are troughs, which are configured to receive the wires of a cable that has been inserted through the opening. Slots are provided adjacent the front termination end. The slots communicate with the troughs and are configured for receiving metallic contacts in a direction perpendicular to the troughs. The metallic contacts of the plug, once received in the slots, establish electrical communication with the cable wires that are in the troughs. The slots are open at the top of the plug housing, opposite the troughs, and are also open at the front end of the housing.
In terminating a cable to a modular plug, the jacket of the cable is stripped from an end portion of the cable. The stripped portion is inserted through the rear opening of the plug housing with the cable wires received into the troughs. The cable is then fixed with respect to the plug and the plug is positioned on an apparatus that is used for inserting the contacts into the plug housing. Once the metallic contacts are seated within the slots, an apparatus that includes an actuated ram applies a downward force in moving and causing the seated contacts to engage the wires that are within the troughs.
According to other methods, the contacts may also be partially pre-inserted into the plug housing prior to the insertion of the cable wires and then fully crimped down thereafter.
Each metal contact normally defines blades that are configured to pierce the insulation of a wire at a first end of the contact. The opposite second end of the metal contact normally defines a flat surface that is configured to be engaged by the ram for driving the contact into the plug housing. When the contacts are fully inserted into the plug housing, the blades of the contacts pierce the insulation and engage the wires of the cable to provide an electrical connection.
When each metal contact is fully inserted into the plug housing and engaged with the wires, a portion of the contact is positioned within the plug housing and not exposed to the exterior of the housing and a portion of the contact (e.g., a portion that includes the second end) is exposed to an exterior of the plug housing. The exposed portion of the contact resides within the slot but communicates with the exterior of the plug housing due to the slot opening at the top and the slot opening at the front of the plug housing.
When the plug is inserted into a jack cavity, the exposed portions of the contacts within the slots are adapted to engage corresponding conductors within the jack cavity and complete the electrical connection from the wires of the cable to the jack.
The second end of the plug contact that includes the flat surface (used for engagement with the ram) normally also defines rounded surfaces adjacent both the front and the rear of the contact. The contact is normally symmetrical with respect to an axis which extends through its center of gravity and which is normal to the flat surface of the second end. The rounded shape of the surfaces adjacent the front and the rear functions to engage an aligned conductor of a jack into which the plug is inserted. As known, each of the conductors of the jack may extend angularly within the jack cavity and may engage only a portion of the metal contact of the plug (e.g., the rounded front surface).
In manufacturing such contacts for insertion into modular plugs, substantially the entire surface area of the contact is covered with one or more layers of metallic material by a process such as electroplating. One type of metallic material that might be used is nickel, which provides corrosion resistance, smooths out the rough contact material, and prevents diffusion of the contact metal into subsequently deposited layers of other types of metallic material. The nickel layer may then be covered with a relatively thin layer of a precious metal (e.g., gold, palladium nickel, etc.), which enhances connection with the cable wires.
In addition, other selected surface areas of the contact are also covered with an additional layer of the precious metal to enhance the conductivity of the connection with a conductor of the jack. The selected portions may include the rounded surfaces of the second end because they are exposed surfaces and are normally engaged by an aligned jack conductor. The exposed flat surface between the rounded surfaces at the front and rear is also normally covered since this surface might also come into contact with the jack conductors. When providing the additional layer of the precious metal for enhanced conductivity, a relatively small portion of each flat side surface of the contact might also be covered due to the plating process.
Cost savings may be realized by reducing the areas of a contact which are covered with the precious metal (such as gold or palladium nickel), particularly in view of the large number of plugs which are manufactured each year. Improved designs of contacts which might provide for such cost savings without sacrificing performance and/or manufacturability are desired.